Electromagnetic relay



Dec. 5, 1950 A. R. YOUNG ELECTROMAGNETIC RELAY Filed Aug. 19, 1946 INVENTOR. Arthur R. Young BY 0.41M, WM M (014/,

ATTORNEYS Patented Dec. 5, 1950 ELECTROMAGNETIC RELAY Arthur R. Young, Rockford, lIlL, assignor to Barber-Colman Company, Rockford, 111., a corporation of Illinois Application August 19, 1946, Serial No. 691,642

6 Claims. 1

This invention relates to a sensitive magnetic relay by which switchin is actuated in response to energization of a rotary electric motor.

One object is to provide a relay of the above character embodying novel means for preventing false operation of the switch in response to momentary energization of the motor.

A more detailed object is to provide a novelly arranged lost motion connection between the motor and the switch actuator.

Another object is to provide a relay of the above character having a novel means for reducing the acceleration of the motor.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which Figure 1 is a plan view of a relay embodying the novel features of the present invention.

Fig. 2 is a fragmentary sectional view taken along the line 22 of Fig. 1.

Fig. 3 is an enlarged fragmentary end elevational view, looking from the right-hand side of Fig. 1.

Fig. 4 is a fragmentary sectional View taken along the line 4-4 of Fig. 2.

In the form shown in the drawings, the motor of the improved relay is of the shaded pole induction type comprising a stator 5 having a field coil 6 continuously energized by alternating current and two poles enclosing a squirrel cage rotor I on a shaft l2 which is journaled in bearings 3 mounted in side plates on the stator. Four multiple turn shading coils 9 and I9 enclosin side portions of the motor poles adjacent the rotor are arranged to be short-circuited in diagonally opposite pairs to initiate turning of the rotor in opposite directions. Herein, the motor stator is supported on a plate II, which, in this instance, forms an upstanding leg of a U-shaped bracket.

Mounted on the bracket on opposite sides of the shaft l2 are two so-called microswitches l3 and M which are closed by depression of their actuating pins l 5 by spring arms is carrying rollers H and i8. These rollers constitute the followers of a cam [9 having outwardly diverging sides 23 and an arcuate end 21 which constitutes a dwell of substantial extent. The cam comprises a U-shaped metal piece loose on a stud 22 pro-- .iecting outwardly from the bracket. A contracarcuate surface 2! of the cam engaging the roller 5 as the cam reaches the limit position shown in phantom Fig. 3.

The cam. is actuated b the motor through speed decreasing gearing and lost motion connections arranged to prevent actuation of either switch in response to momentary energization of the motor. The bearing includes a pinion 24 fast on the motor shaft and meshing with a gear 25 loose on the stud 22 between the bracket l l and the earn 59. A pin 26 projecting from the gear 25 is adapted to engage a crossarm 21 on the cam member after a lost motion of nearly a quarter revolution. After turning of the crossarm through ninety degrees, the other end 28 of the pin 25 engages a stop 29 (see 4) struck out of the bracket ll thereby limiting the turning cam and crossarm in the positions shown in phantom in Fig. 3. In this movement and substantially before the end thereof, one side 2c of the cam moves the follower roller far enough to actuate and close one switch after which the dwell surface 2i is presented to the roller so that the cam overruns the point of switch closure before the stop 29 is encountered. During the over-' travel and also in the corresponding reverse movement of the cam, the dwell 2! holds the switch closed without increasing the actuating force applied thereto.

When the motor torque is released other than momentarily, the spring 23 returns the cam memher is to neutral position, the gear 25 running ahead of the crossarm 2'! and coastin with the rotor i to some point intermediate that at which the pin 25 leaves the crossarm on one side and,

strikes the crossarm on the other side. By virtue of the lost vmotion, the possibility of the actuator pin 26 overrunning sufficiently to engage the cross-arm and actuate the other switch is avoided.

By virtue of the cam dwell 2| and the overrunning of the switch actuating position by the 3 cam, the switch will not open in response to momentary deenergization of the motor. That is to say, during the initial return movem nt of h duration corresponding to a momentary opening of the motor circuit, the follower would not ride off from the dwell, and therefore the switch would remain closed. As a result, the relay switch will remain closed during the chattering of the control switch by which the motor circuit is governed.

Means is provided for reducing the acceleration of the motor shaft so as to prevent effective closure of the relay switch in response to momentary energization of the motor such as may be caused by vibration or other transient conditions affecting the sensitive relay by which the motor is usually controlled. Herein, this means comprises a small flywheel 3!! loose on the other end of the motor shaft l2 and having a slip friction connection therewith. This clutch connection comprises a disk 3| fast on the motor shaft and engageable frictionally with one side of the flywheel. A disk 32 engageable frictionally with the other side of the flywheel is loosely splined on a collar 33 fixed by a screw 34 to and axially adjustable along the shaft I2. A compression spring 35 acts between the collar and the disk 32 to press the disks against the flywheel under pressure determined by the strength of the spring 35. The latter may be varied by adjustment of the collar 34 along the shaft.

The adjusted stress of the spring 35 is such that norm-ally only a slight slippage of the clutch occurs during normal starting of the motor. Thus, acceleration of the rotor is resisted by the flywheel thereby prolonging the time between the energization of the motor and the ultimate closure of one of the switches. When, after closure of the switch, the motion of the gear '25 is arrested by the stop 29, the clutch slips, permitting the flywheel to overrun the rotor instead of causing rebounding from the stop with a consequent danger of opening of the switch. That is to say, during such overrunning of the flywheel, a torque is applied frictionally to the rotor shaft in a direction to hold the gear 25 in switch closing position against the stop 29.

A second function of the fr ction coupled flywheel is to assist the cam dwell ill in preventing opening of a closed switch in response to momentary opening of the motor c rcuit. This is due to the inertia added by the flywheel in delaying the return motion of the rotor I.

By virtue of the lost motion connections be tween the gear 25 and the cam l9 on the one hand and between the cam and the follower roller on the other hand, combined with the speed reduction gearing and the acceleration reducing effect of the flywheel, it will be apparent that effective closure of either switch is delayed for some time after initial energization of the motor. Thus, the relay does not respond to momentary closure of the motor c rcuit or other conditions which make such response of the relay undesirable.

I claim as my invention:

1. An electromagnetic relay comprising an electric motor having a rotary shaft with a p nion thereon, a rotary gear meshing with said pinion, a pair of switches, means for actuating the respective switches in response to turning of said second gear by said motor in opposite directions away from a predetermined position, yieldable means for returning said gear to and normauy maintaining the same in said prede- 4 termined position, a flywheel loose on said motor shaft, a friction clutch coupling said shaft and said flywheel, the latter being rotatable with the driven element of said clutch so as to be adapted to overrun said motor by slippage of the clutch, and means yieldably maintaining said clutch constantly engaged.

2. An electromagnetic relay comprising a rotary member, spring means resisting turning of said member in opposite directions away from a neutral position, stop means limiting the turning of said member in opposite directions, switch means respectively actuated in response to turning of said member to its opposite limit positions, a reversible electric motor energizable selectively to turn said member in opposite directions, and means for reducing the acceleration of said member in response to momentary impulses comprising a flywheel mounted loosely on said member for rotation relative thereto and a slip connection coupling said flywheel and said member and frictionally resisting relative turning of the two.

3. An electromagnetic relay comprising an electric motor having a rotor adapted to turn in response to energization of a winding of the motor, a member rotatable with said rotor, a cam having a rotary lost motion connection with said member and spring urged toward a neutral position, switches adapted to be actuated in response to turning of said cam to limit positions in opposite directions away from said position, and a flywheel having a slip friction connection with said rotor.

4. An electromagnetic relay comprising a reversible electric motor having a rotary shaft, yieldable means urging said shaft toward a pre determined position, a pair of switches, means having lost motion connections with said shaft and operable to actuate the respective switches after turning of said shaft through limited angles away from said position, whereby to prevent actuation of the switches in response to momentary energization of sad motor, said ac tuating means including followers connected to said switches, a rotary cam operable to move said followers and actuate the associated switches after a predetermined movement in either direction away from a neutral position, said cam hav ng a dwell surface engaging the actuated follower after actuation of the switch whereby to perm t the cam to overrun the switch actuating position and hold the switch actuated, and means for limiting the motion of the cam after a predetermined overrunning of either switch actuating position,

5. An electromagnetic relay comprising an electric motor having a rotor adapted to turn in response to energization of a winding of the motor, a member rotatable with said rotor, a rotary element spring urged toward a neutral position and having a rotary lost motion connection with said member, switches adapted to be actuated in response to turning of said element to limit positions in either direction away from said neutral position, a flywheel loosely mounted on said rotor for rotation relative thereto, and a friction clutch coupling said flywheel and sa d rotor and having continuously engaged relatively rotatable elements.

6. An electromagnetic relay comprising an electric motor having a rotor adapted to turn in response to energization of a winding of the motor, a member rotatable with said rotor, a rotary element spring urged toward a neutral position and having a rotary lost motion connec- REFERENCES CITED tion with said member, a pair of switches, means a providing a 10st motion connection between said my}; gig gg fs are-[0f record in the element and said switches to actuate one of the v latter in response to turning of said element pre- 5 UNITED STATES W determined distances in either direction away Nu b r Name Dat from said neutral position, a flywheel loosely 708,007 Ball Sept. 2, 1902 mounted on said rotor for rotation relative 1,335,418 Barnum Mar. 30, 1920 thereto, and a friction clutch coupling said rotor 1,585,318 Tupper May 18, 1926 and said flywheel and having cont nuously 10 1,801,699 Trager Apr. 21, 1931 eased relativ ly rotatable lements. 2,068,402 Dufling et a1 Jan. 19, 1937 q '2,174,275 Raney Sept. 26, 1939 ARTHUR YOUNG- 2,177,400 Almquist Oct. 24, 1939 1 2,430,367 Pudelko et a1. Nov. 4, 1947 

